System for dual frequency range mobile two-way satellite communications

ABSTRACT

A microwave antenna terminal for two-way, in-motion communication systems using geostationary or other orbit satellites, and capable of supporting two-way communication in two different frequency ranges, for example Ku and Ka frequency ranges, is provided.

PRIORITY CLAIM

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 61/843,216, filed Jul. 5, 2013, and entitled “SYSTEM FOR DUALFREQUENCY RANGE MOBILE TWO-WAY SATELLITE COMMUNICATIONS,” the disclosureof which is incorporated by reference herein in its entirety and madepart hereof.

BACKGROUND

Systems and technologies existing in the art include different types ofantenna terminals based on reflector antennas or antenna array panelssuch as VSAT two-way fixed-service terminals, transportable VSAT systemsand low-profile in-motion receive-only or two-way systems, based onplanar-array antenna technology. Antenna array technology has a decisiveadvantage in mobile systems allowing achievement of a low-profileantenna terminal, which may be applicable to small, land-based vehiclesand may support different types of broadband services, such as live TVreception, Internet, and high-speed data communications. For example,such a mobile system is disclosed in U.S. Pat. No. 7,379,707 to DiFonzoet al., entitled “System for concurrent mobile two-way datacommunication and TV reception,” which describes a mobile terminalsystem that supports a combination of concurrent two-way datacommunication and television reception capabilities for commercial,recreational and other activities. One disadvantage of availabletechnologies is their inability to support mobile services in differentfrequency ranges using one common terminal.

The drastically increased need of higher speed broadband communicationshas prompted the expansion of traditionally used frequency ranges (C andKu) to include higher frequencies, for example, such as Ka frequencyrange (19-30 GHz) in addition to the traditionally used Ku range(10.9-14.5 GHz). In order to satisfy demand, a large fleet ofgeostationary high communication capacity Ka frequency range satelliteswas launched recently. These satellites are capable of supporting a widerange of communication services including broadband Internetconnectivity for fixed and mobile users.

SUMMARY

The present disclosure concerns a microwave antenna terminal applicableto two-way, in-motion communication systems using geostationary or otherorbit satellites, and capable of supporting two-way communication in twodifferent frequency ranges. For example, Ku and Ka frequency ranges.

In accordance with aspects of the disclosure, a low-profile, mobile,in-motion antenna and transmit/receive terminal system for two-waycommunication, capable of supporting services in two different frequencyranges provided by satellites on different orbital positions isprovided. Satellites may provide services in Ku and Ka band frequencyranges but under certain circumstances only one frequency range may beoperative at a time.

In accordance with one or more aspects, frequency ranges and satellitepositions may be switched and/or adjusted in a fast and fully automatedmanner. In some embodiments, components ensuring operation in thedifferent frequency ranges are initially preinstalled and no humaninteraction may be needed during the process of switching and/oradjusting ranges and/or positions.

In some embodiments, polarization control capabilities for differentfrequency ranges are provided. For example, switching between circularpolarizations and precise tuning of linear polarization may be performedin a fully automated manner, depending on the terminal and satelliteposition, as well as the current value of the mobile platform tiltangle.

In some embodiments, one or more required satellites may be trackedusing an advanced navigation system. In some embodiments, such anadvanced navigation system may include three-axis gyros and/oraccelerometers, a temperature sensor (e.g., for temperature drifterrors), and/or a differential GPS receiver.

In some embodiments, the tracking system may include a digital trackingreceiver integrated into the outdoor unit, which may provide fast andaccurate signal strength feedback without need for feedback from theindoor receiver for reacquisition.

In some embodiments, a dual-range, optimized radome and highlyintegrated indoor unit may provide biasing and control to electronicblocks integrated into the outdoor unit, and may ensure accurate andreliable system operation.

In some embodiments, the system may be optimized for specific poweramplifiers, for example, a block up converter may be shaped to ensureminimal footprint and/or a compact outlook.

This summary is not intended to identify critical or essential featuresof the disclosure, but merely to summarize certain features andvariations thereof. Other details and features will be described in thesections that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

Some features herein are illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings, in whichlike reference numerals refer to similar elements, and in which:

FIG. 1 depicts an illustrative communication system in accordance withone or more aspects of the disclosure;

FIG. 2 depicts an illustrative construction in accordance with one ormore aspects of the disclosure;

FIG. 3 is a block diagram of an illustrative mobile antenna terminal inaccordance with one or more aspects of the disclosure;

FIG. 4 a depicts an illustrative configuration of a dual-port arrayantenna element of a Ku frequency range operative panel in accordancewith one or more aspects of the disclosure;

FIG. 4 b depicts an illustrative configuration ofhorizontal-polarization differential-feed probes in accordance with oneor more aspects of the disclosure;

FIG. 4 c depicts an illustrative configuration of vertical-polarizationdifferential-feed probes in accordance with one or more aspects of thedisclosure;

FIG. 5 a depicts an illustrative four-to-one suspended strip linecombining circuit for horizontal-polarization port combining inaccordance with one or more aspects of the disclosure;

FIG. 5 b depicts an illustrative four-to-one suspended strip linecombining circuit for vertical-polarization port combining in accordancewith one or more aspects of the disclosure;

FIG. 6 a depicts an illustrative configuration of a horizontal-portsuspended strip line combining circuit in accordance with one or moreaspects of the disclosure;

FIG. 6 b depicts an illustrative configuration of a vertical-portsuspended strip line combining circuit in accordance with one or moreaspects of the disclosure;

FIG. 7 depicts an illustrative suspended strip line to waveguidetransition in accordance with one or more aspects of the disclosure;

FIG. 8 depicts an illustrative final antenna panel waveguide combiner inaccordance with one or more aspects of the disclosure;

FIG. 9 depicts an illustrative dual-band-range antenna array element foruse in a Ka frequency range operative panel in accordance with one ormore aspects of the disclosure;

FIG. 10 is a block diagram depicting an illustrative satellite trackingand acquisition system in accordance with one or more aspects of thedisclosure;

FIG. 11 is a block diagram depicting an illustrative multi-mode signaldetector in accordance with one or more aspects of the disclosure;

FIG. 12 depicts illustrative data processing of digital data provided bya multi-mode signal detector in accordance with one or more aspects ofthe disclosure;

FIG. 13 depicts an illustrative satellite-acquisition algorithm inaccordance with one or more aspects of the disclosure;

FIG. 14 depicts an illustrative satellite-tracking algorithm inaccordance with one or more aspects of the disclosure;

FIG. 15 depicts an illustrative polarization-tracking algorithm inaccordance with one or more aspects of the disclosure; and

FIG. 16 depicts an illustrative coordinates-transferring algorithm inaccordance with one or more aspects of the disclosure.

DETAILED DESCRIPTION

In accordance with one or more aspects, a terminal system using alow-profile antenna that is suitable for use with a variety of vehicles,for in-motion satellite communications in support of broadband datatransfer in at least two different frequency ranges and from satelliteslocated in at least two different orbital positions is provided. In someembodiments, the different frequency ranges may be Ku and Ka ranges.With reference to FIG. 1, exemplary system environment 100 may includemobile vehicle 103 which may have low profile antenna terminal system104 mounted thereon. Low profile antenna terminal system 104 may beadapted to communicate with at least two satellites, for example,satellites 101 and 102. At a given time, communications with only one ofthe mentioned satellites may be operative. In some embodiments, anotherexemplary embodiment antenna system may operate with a satellite,comprising transponders, operative either in Ku and Ka frequency rangesor with satellites operative in Ku and Ka frequency ranges located atthe same orbital position. In some embodiments, satellite 101 may beallocated on the geostationary orbit, may be operative in Ku frequencyrange, and may provide FSS (Fixed Satellite Service) in a frequency bandassigned by an appropriate body, such as the Federal CommunicationCommission (FCC) in the U.S. or similar agency in other world regions.This frequency band may be 14.0 to 14.5 GHz for the UPLINK and 11.7 to12.7 GHz for the DOWNLINK. Satellite 102 may be allocated in anotherposition on the geostationary orbit, may be operative in Ka frequencyrange, and may support broadband two-way service. The operativefrequency bands in Ka frequency range may be 29 to 31 GHz for the UPLINKand 19 to 21 GHz for the DOWNLINK. Switching between these twosatellites, operative in different frequency ranges, may be doneautomatically by low-profile antenna terminal 104. Equipment forswitching between satellite positions and frequency ranges may bepre-installed initially within the terminal outdoor unit, with no needfor subsequent human interaction.

FIG. 2 depicts an illustrative construction of an outdoor unit inaccordance with one or more aspects of the disclosure. Outdoor unit 200may comprise at least two separate antennas, for example, antennas 202and 201, which may be operative in at least two different frequencyranges. These two antennas may be antenna arrays arranged as flat panelsin order to ensure a low profile of outdoor unit 200. The low-profileantennas may be preferable for mobile systems, for example, in order tosupport mounting on small land based vehicles. Another advantage oflow-profile antennas is their ability to be flush mounted on a vehicle'sroof, for example, to maintain vehicle mobility, agility, stability,and/or aerodynamics, and/or avoiding marking the equipped vehicle as ahigh-value target for enemy attack (e.g., in the context of militaryapplications).

As illustrated in FIG. 2, in some embodiments, antenna panels 201 and202 may be mounted back-to-back onto a rotating platform 204, and may berotated in azimuth and elevation in order to point an antenna beam to aparticular satellite. One of the panels, for example panel 201, may beoperative in transmit/receive mode in Ku frequency rage, while another,for example panel 202, may be operative in transmit/receive mode in Kafrequency range. In some embodiments, panel 201 and/or panel 202 may bemade of at least one or more plastic materials, and/or may comprise aconductive coating. The antenna terminal may be mounted on stationarybase plate 203, which may be attached to the vehicle using mountingdampers 205. In some embodiments, a block up converter operative intransmit mode may be mounted below base plate 203 and connected bywaveguide inputs 207 and 208. In some embodiments, waveguide inputs 207and 208 may be operative in Ku and Ka frequency ranges. For exampleinput 208 may be operative in Ku frequency range, while input 207 may beoperative in Ka frequency range. Microwave signals may be transferred torotating platform 204 using waveguide rotary joint 206. In someembodiments, the antenna terminal may comprise a satellite-recognitionand tracking system for finding and/or tracking a desired satellite.This system may comprise one or more gyroscopic sensors, a tilt sensor,an integrated digital signal receiver, and/or GPS receiver 210, any ofwhich may be controlled by a central CPU (Central Processing Unit) withembedded software.

FIG. 3 depicts an illustrative antenna terminal (outdoor unit) inaccordance with one or more aspects. With the reference to FIG. 3, partsof the antenna terminal may be mounted on static platform 2 or rotatingplatform 1 platforms. On rotating platform 1, at least two antennapanels (e.g., flat array antennas) may be mounted. For example, antennapanel 3 may be operative in Ku frequency range and/or antenna panel 4may be operative in Ka frequency range. In some embodiments, both panels3 and 4 may be operative in transmit and receive modes and may compriseany of an embedded diplexer and polarization control circuitry.Polarization switching and control circuitry may be controlled bycentral processing unit (CPU) 14 by slip ring transitions 15. RF signalsmay be transferred between panels 3 and 4, and RF electronics, installedon the rotary platform 1, using waveguide elevation rotary joints inorder to achieve lower losses and higher reliability. In someembodiments, RF signals may be transferred to antenna panel 3, operativein Ku frequency range, by elevation waveguide rotary joints 17 and 18.For example, rotary joint 17 may be operative in Ku transmit frequencyband and rotary joint 18 may be operative in Ku receive frequency band.In some embodiments, RF signals may be transferred to antenna panel 4,operative in Ka frequency range, by waveguide rotary joints 19 and 20.For example, rotary joint 20 may be operative in Ka transmit frequencyband and rotary joint 19 may be operative in Ka receive frequency band.In some embodiments, the receive signals may be transferred to LNBs (LowNoise Blocks) 8 and 7. For example, LNB 8 may be operative in Ku receivefrequency band and LNB 7 in Ka receive frequency band. Both LNBs may becontrolled by the central processor, and may output IF (IntermediateFrequency) signals in L band to be transferred by azimuthal rotary joint22 to static platform 2, and then to VSAT modem 16.

The transmit signals may be delivered by block up convertors (BUCs) 10and 11. For example, BUC 10 may generate signals in the Ku transmitfrequency range, while BUC 11 may generate signals in the Ka transmitfrequency band. The signals may be transferred to static platform 2 byazimuthal waveguide rotary joints 23 and 21. For example, rotary joint23 may be operative in Ku transmit frequency band, while rotary joint 21may be operative in Ka transmit frequency band.

In some embodiments, antenna panels 3 and 4 may be pointed toward aparticular satellite in azimuthal plane by azimuthal motor 9, which maycomprise an embedded motor controller, controlled by CPU 14. In someembodiments, each of the panels 3 and 4 may be pointed toward theparticular satellite in elevation plane using a separate motor. Forexample, elevation motor 5 may be operative for elevation-plane pointingof the Ku-frequency-range antenna panel 3, while motor 6 may beoperative for elevation-plane pointing of the Ka-frequency-range panel4.

In some embodiments, the satellite acquisition and tracking system maycomprise sensor block 12. Sensor block 12 may comprise gyroscopicsensors, an integrated digital receiver, and/or a differential GPSreceiver in order to deliver information to CPU 14 for satelliteacquisition, reacquisition, and/or tracking.

In some embodiments, Ku-frequency-range panel 3 may comprise an antennaarray of radiating square apertures (e.g., open-ended waveguideradiating elements having strip-line feeds) operative for horizontal andvertical, linearly polarized signals. With reference to FIG. 4 a, insome embodiments, an antenna array element may comprise a grid layer302, forming a square-radiating aperture 301, that may be fed by atriple transformer 303, wherein the transformer 303 may comprisequad-ridged waveguide sections for at least the purpose of achievinggood matching over both transmit and receive Ku frequency bands. Theantenna element horizontal-polarization port may be operational in afirst fundamental mode and may be fed by differential probes 304. Theantenna element vertical-polarization port may be operational in asecond fundamental mode, and may be fed by differential probe 305. Thedifferential excitation (stimulation) of the quad-ridged waveguidesections 303 may provide good performance (e.g., low loss and goodmatching) of the open-ended waveguide radiating elements over the entireoperative frequency range, e.g., due to effectively suppressingundesired high-order electromagnetic modes. Stimulation of the twofundamental modes may be accomplished by two sets of orthogonallyoriented differential probes 304 and 305 which may be placed ondifferent levels, e.g., one above the other as depicted in FIG. 4 a. Thefirst fundamental mode may be excited by the first set of differentialprobes 304 in the quad-ridged waveguide 303, which may be placed on afirst level. A back-short for the first fundamental mode may be providedby a double-ridged waveguide section 320, which may be connected betweenthe first and second levels of the probes. The second fundamental modemay be stimulated through the second set of differential probes 305,which may excite the double-ridged waveguide section 320. A squarewaveguide section 330 beneath the double-ridged waveguide section 320may be configured to provide a back-short for the second fundamentalmode. FIG. 4 b depicts an illustrative horizontal-port differentialprobe construction. The construction may comprise two differentialsuspended strip line probes 306 loaded by a capacitance 308 andparasitic coupled stub 307 for perfect matching through entire operatingfrequency range. FIG. 4 c depicts an illustrative vertical portdifferential probe construction. The construction may comprise twodifferentially fed probes 308 matched by capacitance 311, ring line 310and a parasitically coupled stub 309.

In some embodiments, antenna element horizontal and vertical ports arecombined by two independent combining circuits and fed to the twoindependent antenna outputs allowing for the application of polarizationcontrol. Each one of these two independent combining circuits maycomprise two stages of combining (e.g., initial combining by a suspendedstrip line combining circuit, and a final waveguide base combiningcircuit). This two-stage construction of the antenna combining circuitsmay significantly reduce the complexity and/or final thickness of theantenna panel, keep losses relatively low, and/or ensure high antennaefficiency.

FIG. 6 a and FIG. 6 b depict illustrative configurations of initialcombing circuits in accordance with one or more embodiments. The combingcircuit for horizontal ports 600 a is illustrated by FIG. 6 a while thecombing circuit for vertical ports 600 b is illustrated by FIG. 6 b.Both combing circuits comprise four-to-one combing circuits that arethen combined by T junction combiners. For example, combing circuit 600a comprises suspended strip line T junction 601 to combine four-to-onecombing circuits and suspended-strip-line-to-waveguide transitions 603.The second combing circuit, for vertical ports combining, may similarlycomprise suspended strip line T junctions 602 andsuspended-strip-line-to-waveguide transitions 604.

FIGS. 5 a and 5 b depict illustrative four-to-one combing circuits forcombining antenna elements horizontal and vertical polarization ports.Four-to-one combing circuit 400 for horizontal ports is illustrated byFIG. 5 a. The differential ports of the four antenna array elements arefed by four rat-race-suspended strip-line couplers 401, while the finalsummation is made by another rat-race coupler 402, and then the summedsignal is fed to combining-circuit output 403.

FIG. 5 b depicts an illustrative four-to-one combing circuit forvertical antenna elements.

Combing circuit 500 comprises four suspended-strip-line rat-racecouplers 501 and a final rat-race coupler 502. Then the signal istransferred to the vertical-polarization port-combiner output 503.

FIG. 7 depicts an illustrative configuration of T junction combiners 701and suspended-strip-line-to-waveguide transitions 702. A step waveguideimpedance transformer 704 may be used for better matching.

FIG. 8 depicts an illustrative configuration of final waveguide basedcombiner 800. Final waveguide combiners for horizontal antenna ports 805and for vertical antenna ports 802 comprise waveguide T junction 803 andwaveguide impedance step transformers 804. The summed signal istransferred to the horizontal antenna port 805 and correspondently tovertical antenna port 806.

With reference to FIG. 9, in some embodiments, dual-band antenna element900 may be used to build a Ka-frequency-range operative panel. Antennaelement 900 comprises dielectric thin cap 901, radiating aperture grid902, square quad-ridged (open ended) waveguide 903 and septum 904. Insome embodiments, the square quad-ridged (open ended) waveguides may bespaced in less than one wavelength from each other. A square quad-ridged(open ended) waveguide 903 is used for at least the purpose ofsupporting dual band operation in Ka frequency range. For example, thefirst band may be 19 to 21 GHz and the second may be 29 to 31 GHz. Theabove-mentioned square quad-ridged (open ended) waveguide in combinationwith the septum 904 may form a polarization-forming device, formingcircularly polarized signals with RH (right hand) and LH (left hand)polarization fed to two rectangular waveguide outputs 905. The antennaelements outputs may be summed by to independent waveguide-combiningnetworks.

In some embodiments, a system for satellite acquisition and tracking maycomprise a combination of open loop and close loop tracking systems inorder to achieve better accuracy at lower cost. The open loop system maybe used for fast platform movement compensation, while the close loopsystem, may comprise a Receive Signal Strength Indicator (RSSI), whichmay be used for satellite acquisition and reacquisition and/or for openloop sensors drift compensation.

FIG. 10 depicts an illustrative antenna terminal acquisition andtracking system. The signal received by antenna panel 1001 may bedown-converted by a Low Noise Block (LNB), divided by splitter 1003 andtransferred to the receiver and to multi-mode signal detector 1016.Multi-mode signal detector 1016 may have an adjustable frequency band ofoperation and may be used as a beacon receiver in the process of thesatellite acquisition and as an RSSI detector in the process of thesatellite tracking. In some embodiments, the multi-mode signal detectormay comprise zero-IF tuner 1004, temperature stabilized oscillator(TCXO) 1005, anti-aliasing filter 1006 and two-chained Analog-to-DigitalConverters (ADCs) 1007. Information regarding the signal strength may betransferred to CPU 1008. CPU 1008 may process this information inparallel to the information received by internal Attitude HeadingReference System (AHRS) 1013 in the process of satellite acquisition andreacquisition or in parallel to the information received by inertialsensors 1012 in the process of the satellite tracking. The calculatedinformation about the antenna beam position may then be transferred tothe motor controller 1009, which may drive azimuth motor 1010 and/orelevation motors 1011 in order to point the beam of antenna panel 1001toward a particular satellite. Additionally or alternatively,information from external Inertial Navigation System (INS) 1014 and/orexternal beacon receiver 1015 may be utilized.

The configuration and the operation of multi-mode signal detector 1016are described in further detail with reference to FIG. 11. The detectormay be configured to measure RF signal strength in a bandwidth varyingfrom as low as 1000 Hz to as high as tens of MHz centered on a certainfrequency of interest (e.g., f₀). In some embodiments, the RF signal isdown converted to the base band by tuner 1101 and switched bymultiplexers 1102 and 1107 to one of the following devices:

-   -   Directly to the input of the logarithmic detector 1108 in order        to provide signal detection over the entire base band bandwidth        (for example from several MHz to tens of MHz);    -   Passed to the input of a programmable baseband low-pass filter        1106 and then to the input of the logarithmic detector 1108 in        order to vary the signal detection bandwidth from tens KHz to        several MHz; or    -   Passed through buffer and antialiasing filter 1103 to the input        of an analog to digital converter ADC 1105, and then processed        by the CPU or Digital Signal Processor (DSP).

FIG. 12 depicts illustrative data processing in accordance with thethird option, and may comprise the processes of widowing 1201 of thesampling data in order to minimize the effect of spectral leakage duringthe next processing, Fast Fourier Transformation (FFT) 1202 in order tocompute the signal spectrum, power magnitude computation 1203, optionalnon coherent averaging 1204, peak searching 1205, and converting of thepower level in logarithmic units 1206.

In some embodiments, particular methods of satellite acquisition areutilized in order to significantly reduce acquisition and reacquisitiontime. Since the uncertainty in the satellite beacon frequency istypically bigger than the allowable offset of communication transponderfrequency, the searching may be done in overlapping frequency intervalsby changing the tuner frequency. From another side the beaconfrequencies are not unique and may be reused over several satellites inthe sky and in that case the beacon signals cannot identify that therequired satellite is acquired. In this case additional satelliteverification may be done using an Attitude Heading Reference System(AHRS). Unfortunately, available AHRSs are not capable of providing therequired accuracy sufficient for open loop “blind” pointing of theantenna. In order to solve this problem, in some embodiments, acombination of an attitude heading reference system and multi-modesignal detector (e.g., working in a narrow band mode as beacon receiver)may be utilized.

FIG. 13 depicts an illustrative satellite acquisition algorithm.Referring to FIG. 13, the depicted satellite searching algorithm may bedescribed as follows:

The tuner is set initially on f_(t)=f_(start)=f₀−(f_(s)/4), where f₀ isthe last known beacon frequency, f_(t) is the tuner frequency, and f_(s)is a sampling frequency of the ADC. For initial antenna usage this maybe the nominal beacon frequency according to the satellite datasheet.Once the antenna acquires the satellite, f₀ may be replaced by theactual found frequency. In this way, the expected frequency of thebeacon may be centered in one of the continuous FFT sub-bands.

The AHRS may require some interval after the power up for cold start(typically 60 seconds). Before AHRS is locked, the last known GPScoordinates may be used to calculate the expected satellite elevation.The orientation of the antenna referenced to true North may be unknown,and the searching may be started over the whole azimuth range of 360°(long cycle). After each FFT processing a peak in the spectrum may besearched in the ranges [−f_(s)/2, f_(s)/2] centered on the tunerfrequency f_(t).

When the cold-start interval of the AHRS has passed, the AHRS mayprovide the orientation of the antenna referenced to true North, whereinthe provided orientation may include some uncertainty (Δ_(Head)). Theantenna CPU 1008 may be configured to perform a coordinatetransformation from the Earth Centered East Down (ECEF) coordinatesystem to the antenna coordinate system, and may calculate the expectedsatellite heading and elevation. CPU 1008 may then control a movement ofthe antenna, e.g. movement at a maximal velocity, to (Heading−Δ_(Head))coordinate. The search for the satellite may then be limited in theazimuth range [Heading−Δ_(nead), Heading+Δ_(Head)] (short cycle). If along or short cycle is finished without finding a peak, the tunerfrequency may be changed by Δf and a new cycle may be started. In thecase of a short cycle, the motion direction may be reversed, so thesearching may be done only in the azimuth range [Heading−Δ_(Head),Heading+Δ_(Head)].

When a peak is found, a backward coordinate transformation may beperformed from the antenna coordinate system to the ECEF system tocalculate the orbital position of the received satellite from the actualazimuth, elevation, and antenna platform inclination. If the calculatedorbital position matches the expected value within a predefineduncertainty range, then the detected beacon frequency may be stored in anon-volatile memory to be used the next time the antenna is powered up.If the orbital position does not match, then the searching cycle may berestarted.

In some embodiments, two possible methods of satellite tracking may beapplicable:

-   -   Close loop tracking—using information from the inertial system        sensors and from RSSI detector; and    -   Open loop tracking—using an external high accuracy inertial        navigation system.

FIG. 14 depicts an illustrative algorithm for close loop satellitetracking and FIG. 15 depicts an illustrative algorithm for polarizationtracking Referring to FIGS. 14 and 15, the tracking method may bedescribed as follows:

The satellite tracking may be started after the satellite is found bythe satellite acquisition process. A coordinate transformation may beperformed to produce azimuth and elevation angular velocities from thesignals of 3 gyros aligned with the axes of the antenna coordinatesystem. The angular velocities may then be integrated to obtain theazimuth and elevation angles of the disturbances in the antennaorientation. The PID loops for azimuth and elevation may be used tocontrol the motors in a way to cancel the measured disturbances.

The azimuth and elevation angles may be moved (dithered) by orthogonalfunctions with small amplitudes (sine-cosine) and the signal detectorlevel (RSSI) may be measured synchronously with the motion. Theintegrated asymmetry in the detected signal may be used to compensatethe antenna orientation in a way to cancel this asymmetry and forestimation of gyroscope drift.

As azimuth and elevation channels provide only two degrees of freedomfor gyroscope compensation, additional error estimation may be performedfrom the orientation of the gravity vector measured by the 3-axisaccelerometer.

In some embodiments, open loop tracking using a high accuracy externalinertial navigation system (INS) for providing direct pointing to thesatellite is utilized. The calculations in this case may use therequested satellite orbital position by the user, the INS data (e.g.,roll, pitch, yaw angles and velocities) and antenna geographic locationdata provided by the integrated GPS.

The satellite coordinates may first be calculated in the Earth CenteredEast Forward (ECEF) coordinate system. Then a transformation may beperformed from ECEF to the North East Down (NED) coordinate systemlocated in the geographic position of the antenna. The nexttransformation may calculate the satellite coordinates in the frame ofthe INS coordinate system. Finally, a calculation may be performed forthe satellite coordinates in the antenna coordinate system.

The calculated azimuth, elevation, and polarization may provide commandsto the antenna motors and electronic circuits to align the antenna beamto the satellite.

FIG. 16 depicts an illustrative coordinate transformation algorithm.

The methods and features recited herein may be implemented through anynumber of computer readable media that are able to store computerreadable instructions. Examples of computer readable media that may beused include RAM, ROM, Electrically Erasable Programmable Read-OnlyMemory (EEPROM), flash memory or other memory technology, CD-ROM, DVD,or other optical disk storage, magnetic cassettes, magnetic tape,magnetic storage, and the like.

Additionally or alternatively, in at least some embodiments, the methodsand features recited herein may be implemented through one or moreIntegrated Circuits (ICs). An IC may, for example, be a microprocessorthat accesses programming instructions or other data stored in a ROM. Insome embodiments, a ROM may store program instructions that cause an ICto perform operations according to one or more of the methods describedherein. In some embodiments, one or more of the methods described hereinmay be hardwired into an IC. For example, an IC may comprise anApplication Specific Integrated Circuit (ASIC) having gates and/or otherlogic dedicated to the calculations and other operations describedherein. In still other embodiments, an IC may perform some operationsbased on execution of programming instructions read from ROM or RAM,with other operations hardwired into gates or other logic. Further, anIC may be configured to output image data to a display buffer.

Although specific examples of carrying out the disclosure have beendescribed, those skilled in the art will appreciate that there arenumerous variations and permutations of the above-described apparatusesand methods that are contained within the spirit and scope of thedisclosure as set forth in the appended claims. Additionally, numerousother embodiments, modifications, and variations within the scope andspirit of the appended claims may occur to persons of ordinary skill inthe art from a review of this disclosure. Specifically, one or more ofthe features described herein may be combined with any or all of theother features described herein.

The various features described above are merely non-limiting examples,and may be rearranged, combined, subdivided, omitted, and/or altered inany desired manner. For example, features of the servers may besubdivided among multiple processors and/or computing devices. The truescope of this patent should only be defined by the claims that follow.

What is claimed is:
 1. An apparatus, comprising: a rotating platformcomprising a first antenna panel and a second antenna panel, wherein thefirst antenna panel is configured for transmitting and receiving in afirst frequency band, and wherein the second antenna panel is configuredfor transmitting and receiving in a second frequency band; and a controlsystem comprising a plurality of sensors and at least one processor,wherein the at least one processor is configured to control movement ofthe rotating platform using information received from the plurality ofsensors.
 2. The apparatus of claim 1, wherein at least one of the firstantenna panel or the second antenna panel comprises one or more plasticmaterials and a conductive coating.
 3. The apparatus of claim 1, whereinthe at least one processor is configured to: determine, at a first time,a first position of the rotating platform based on information receivedfrom the plurality of sensors, the first position being suitable, at thefirst time, for communication in the first frequency band via the firstantenna panel; determine, at a second time, a second position of therotating platform based on information received from the plurality ofsensors, the second position being suitable, at the second time, forcommunication in the second frequency band via the second antenna panel;and control the movement of the rotating platform from the firstposition to the second position, wherein the second position isdifferent from the first position and the second time is subsequent tothe first time.
 4. The apparatus of claim 1, wherein the first frequencyband is a Ku frequency band, and wherein the first antenna panelcomprises an array of open-ended waveguide radiating elements havingstrip-line feeds.
 5. The apparatus of claim 4, wherein the open-endedwaveguide radiating elements comprise quad-ridged waveguide sections. 6.The apparatus of claim 4, wherein the first antenna panel comprises astrip-line network and capacitive elements, and wherein the open-endedwaveguide radiating elements are differentially fed from the strip-linenetwork, and matched with the capacitive elements.
 7. The apparatus ofclaim 6, wherein strip-line feeds of the strip-line network are matchedwith ring lines and stubs.
 8. The apparatus of claim 6, wherein thestrip-line network is configured to combine at least one foursome ofdifferentially fed open-ended waveguide radiating elements, and whereinthe strip-line network comprises: a first hybrid-coupling elementconfigured to combine a feed of a first open-ended waveguide radiatingelement of the at least one foursome and a feed of a second open-endedwaveguide radiating element of the at least one foursome into a firstintermediate unbalanced output; a second hybrid-coupling elementconfigured to combine a feed of a third open-ended waveguide radiatingelement of the at least one foursome and a feed of a fourth open-endedwaveguide radiating element of the at least one foursome into a secondintermediate unbalanced output; and a third hybrid-coupling elementconfigured to combine the first intermediate unbalanced output and thesecond intermediate unbalanced output into a combined unbalanced outputfor the at least one foursome of open-ended waveguide radiatingelements.
 9. The apparatus of claim 1, wherein the second frequency bandis a Ka frequency band, and wherein the second antenna panel comprisessquare quad-ridged open-ended waveguides spaced less than one wavelengthfrom each other.
 10. The apparatus of claim 9, wherein the squarequad-ridged open-ended waveguides are configured to transmit and receiveover the bandwidth range of the Ka band.
 11. The apparatus of claim 9,wherein one or more of the square quad-ridged open-ended waveguidescomprise a septum configured as a polarizer.
 12. The apparatus of claim9, wherein the second antenna panel comprises a polarizing layer infront of one or more apertures of the square quad-ridged open-endedwaveguides.
 13. The apparatus of claim 9, wherein the second antennapanel is configured to provide two outputs corresponding to two channelshaving different polarizations.
 14. The apparatus of claim 13, whereinthe second antenna panel further comprises a diplexer configured forseparating the two channels into a receive channel and a transmitchannel.
 15. The apparatus of claim 1, further comprising: a zerointermediate-frequency (IF) tuner configured to receive a signal via atleast one of the first antenna panel or the second antenna panel, andconfigured to provide a down-converted signal; an anti-aliasing filtercoupled to an output of the zero IF tuner, and configured to provide afiltered signal; and a dual-channel analog-to-digital converter (ADC)coupled to an output of the anti-aliasing filter, and configured toprovide samples of the filtered signal to the at least one processor,wherein the at least one processor is configured to use the zero IFtuner, the anti-aliasing filter, and the ADC to detect a narrowbandsignal.
 16. The apparatus of claim 15, wherein the at least oneprocessor is configured to: calculate a Fast Fourier Transform (FFT)using samples of the filtered signal; calculate a signal power magnitudefor each bin of the FFT; and identify a bin of the FFT that correspondsto a maximum signal power magnitude.
 17. The apparatus of claim 15,wherein the at least one processor is configured to search, in parallel,for a satellite carrier signal in frequency range [−f_(s)/2, f_(s)/2]symmetrically located around zero IF tuner frequency (f_(t)), whereinf_(s) represents a sampling frequency of the ADC.
 18. The apparatus ofclaim 15, wherein the at least one processor is configured to search fora satellite beacon frequency using one or more azimuth searching cycles,and to overcome a frequency uncertainty larger than f_(s)/2 in thesatellite beacon frequency by shifting the zero IF tuner frequency(f_(t)) after each azimuth searching cycle.
 19. The apparatus of claim18, wherein the at least one processor is configured to identify asatellite using a combination of a determined satellite beacon frequencyand a satellite heading relative to North.
 20. The apparatus of claim 1,further comprising: a baseband low-pass filter; and a logarithmicdetector, wherein the at least one processor is configured to use thebaseband low-pass filter and the logarithmic detector to detect amedium-bandwidth signal.
 21. The apparatus of claim 19, furthercomprising a switch configured to allow the low-pass filter to bebypassed, wherein the at least one processor is configured to utilizethe switch to bypass the low-pass filter to detect a wide-bandwidthsignal.
 22. The apparatus of claim 1, further comprising a low-precisionattitude heading reference system (AHRS) configured to indicate anantenna heading relative to North, wherein the at least one processor isconfigured to: perform at least one azimuth search cycle for finding asatellite; and use the low-precision AHRS to narrow a search rangecorresponding to the at least one azimuth search cycle.
 23. Theapparatus of claim 22, wherein the at least one processor is configuredto identify a satellite using a combination of a determined satellitebeacon frequency and a satellite heading relative to the North.
 24. Theapparatus of claim 1, wherein the at least one processor is configuredto use information received from an external inertial navigation system(INS) and from a global positioning system (GPS) receiver for pointingat least one of the first antenna panel or the second antenna paneltoward a satellite.
 25. The apparatus of claim 22, wherein the at leastone processor is configured to: convert satellite coordinates to earthcentered earth fixed (ECEF) coordinates; and convert ECEF coordinates tocoordinates corresponding to the rotating platform, and to at least oneof the first antenna panel or the second antenna panel.
 26. A method,comprising: stimulating a first fundamental mode by stimulating asquare, quad-ridged waveguide section using a first set ofdifferential-feeding probes; providing a back-short for the firstfundamental mode using a square, double-ridged waveguide sectionconnected to the quad-ridged waveguide section; stimulating a secondfundamental mode orthogonal to the first fundamental mode by stimulatingthe double-ridged waveguide section using a second set ofdifferential-feeding probes; and providing a back-short for the secondfundamental mode using a square waveguide section connected to thedouble-ridged waveguide section.